1. Field of the Invention
The present invention relates to a liquid processing apparatus for processing substrates, such as semiconductor wafers, by a predetermined liquid process and a liquid processing method to be carried out by the same.
2. Description of the Related Art
A semiconductor device fabricating process uses a liquid processing apparatus that processes semiconductor wafers (hereinafter referred to simply as xe2x80x9cwafersxe2x80x9d), i.e., substrates, by processing liquids, such as chemical liquids and pure water, for cleaning to remove contaminants including particles, organic contaminants and metallic impurities and for etching.
Such a liquid processing apparatus holds a plurality of wafers in a vertical position by a carrying arm, immerses the wafers in a chemical liquid, such as an etch solution, contained in a chemical liquid tank, takes out the wafers from the chemical liquid contained in the chemical liquid tank by the carrying arm, and transfers the wafers to a rinsing tank.
The liquid processing apparatus discharges particles contained in the atmosphere and a mist of the chemical liquid. Therefore, a downflow of clean air is produced in the liquid processing apparatus. It is mentioned in JP-A No. Hei 10-92790 that the clean air flows down along the wafers and it is possible that the wafers are processed irregularly when the wafers are raised into a space in which a downflow of clean air is produced after being immersed in a chemical liquid. When a hydrofluoric acid solution is used as a chemical liquid for an etching process, the hydrofluoric acid solution wetting upper portions of the wafers is dried by the downflow of clean air and the upper portions of the wafers are not etched unsatisfactorily. It is also mentioned in JP-A No. Hei 10-92790 that a cover is disposed above the wafers held by a wafer carrying means so as to screen the wafers from the downflow of clean air to avoid irregular processing due to the downflow of clean air.
Experiments conducted by the inventors of the present invention proved that the wafers are etched still irregularly even if the wafers are screened from the downflow of clean air.
The present invention has been made in view of the foregoing problem and it is therefore an object of the present invention to provide a liquid processing apparatus and a liquid processing method capable of uniformly processing substrates by a liquid process.
It is a first feature of the present invention that a liquid processing apparatus comprising: a processing bath processing a plurality of substrates by processing liquid; a substrate holding device having a substrate holding member capable of holding the plurality of substrates in a vertical position, the substrate holding device being capable of carrying the substrates between the processing bath and an upper position above the processing bath; and a cover placed in a space extending over the substrates held by the substrate holding member of the substrate holding device, the cover covering the space so that any air currents may not be substantially generated around the substrates.
The inventors of the present invention made studies of causes of irregular processing, such as irregular etching, and found that the irregular processing results not only from the effect of a downflow of clean air but also from currents produced around the upper ends of the substrates when the substrates are raised out of the processing liquid after processing the substrates in the processing liquid. The substrates cannot be screened from the currents produced around the same when the substrates are raised out of the processing liquid by simply disposing the cover for screening the substrates from a downflow of clean air, and the currents bias the processing liquid wetting the substrates, causing irregular processing. The present invention surrounds the space extending over the substrates with a cover so that air currents may not be produced in the space to prevent irregular processing by preventing the biasing of the processing liquid wetting the substrate by air currents.
It is a second feature of the present invention that the processing bath contains the processing liquid, the substrates being immersed in the processing liquid to processing substrate, and the substrate holding device carrying the substrates between a processing position where the substrates are immersed in the processing liquid in the processing bath and the upper position.
It is a third feature of the present invention that the liquid process is etching oxidized film formed on the substrate.
It is a fourth feature of the present invention that the cover has a roofing member extending circumferentially in an upper space of the substrates held by the substrate holding member and; end covering members provided on the roofing member, the end covering members being positioned in opposite sides of axial direction of a row of the substrates and in an upper space of the substrates.
It is a fifth feature of the present invention that the cover is formed in a semicylindrical shape by a combination of the roofing member and the end covering member.
It is a sixth feature of the present invention that the cover is formed in a shape of a box by a combination of the roofing member and the end covering member.
It is a seventh feature of the present invention that a lower end of the cover is on a level not higher than upper ends of the substrates.
It is an eighth feature of the present invention that the cover is supported movably upwardly and downwardly against substrates.
It is a ninth feature of the present invention that the substrate holding device is also capable of carrying the substrates between the processing bath and a position beside the processing bath.
It is a tenth feature of the present invention that the substrate holding device includes a pair of support bars capable of substantially horizontally moving toward and away from each other to hold the plurality of substrates therebetween.
It is an eleventh feature of the present invention that a liquid processing method comprising the steps of: processing substrate by processing liquid; raising the substrates out of the processing liquid; and covering a space extending over the substrates with a cover so that any air currents may not be substantially generated in the space extending over the substrates when the substrates are raised out of the processing liquid.
It is a twelfth feature of the present invention that the liquid processing method further comprising the steps of: loading or unloading the substrates on or from a carrying arm; and moving the cover to a position where the cover does not interfere with the substrates and the carrying arm when loading or unloading the substrates on or from the carrying arm.
It is a thirteenth feature of the present invention that the step of covering the space extending over the substrates with the cover includes the steps of: positioning the cover above the substrates before the substrates start emerging from the processing liquid; and raising the substrates and the cover simultaneously so that lower end of the cover is not positioned in a level higher than upper ends of the substrates.